The invention is based on a fuel injection pump for internal combustion engines.
Every pump cylinder of this kind of fuel injection pump must have a recess or niche to receive the control slide, which weakens the overall stability of the pump cylinder and has disadvantages in the event that deformation or slight changes occur during installation of the pump cylinder in the pump housing between the flange and the lower support from tolerance errors, in which case the pump piston guided on either side of this niche in the pump cylinder will no longer slide exactly in alignment. This occurs especially in fuel injection pumps of the kind in which the niche is embodied as an opening or window that penetrates the pump cylinder (German Offenlegungsschrift 34 28 174). Only two connecting pieces remain standing to absorb the axial forces here; the axial forces can be transmitted only via these connecting pieces, and torsion or twisting cannot always be precluded.
However, there are also fuel injection pumps of this generic type (European Patent 0 181 402, FIG. 4), in which the pump cylinder is in two parts, and the niche is produced by axial shaping by metal cutting. Both parts are then joined together again by suitable methods, such as shrinkage or hard soldering, so that the niche is axially closed again by the other part of the pump cylinder. This creates a niche that is open on three sides; the open side is necessary so that the control slide can be engaged by a suitable adjuster in order to adjust it axially on the pump piston. This structural embodiment of the niche has relatively high stability to torsion and twisting of the pump cylinder during installation, but it is very complicated and expensive to manufacture.
Recesses and niches that can be obtained by milling have also been proposed. Once again, however, the complicated production process entails relatively high costs.